Paracyclophanes and in particular [2.2]-paracyclophane derivatives are established ligands for transition metal-catalysed asymmetric reactions (see for example, S. E. Gibson and J. D. Knight, Org. Biomol. Chem., 2003, 1, 1256-1269). Of these, paracyclophane bis(phosphines) have attracted considerable attention because catalysts derived from them show high levels of activity and selectivity in a number of useful asymmetric transformations.
For example, WO 97/47632 describes paracyclophane bis(phosphine) ligands and rhodium (Rh), ruthenium (Ru), iridium (Ir) or palladium (Pd) catalysts derived therefrom for asymmetric hydrogenation, isomerization, hydroboration, cyclization, arylation, alkylation and amination reactions. The ligands described have the formula depicted below;

Where both X groups are the identical, these ligands posses C2 symmetry, that is they are chiral and have a C2 axis of symmetry. For example, the C2-symmetric [2.2] ligand where X=—(CH2CH2)—, known as PHANEPHOS, may be used in the asymmetric hydrogenation of ketones when comprising part of a Ru-diamine complex (see WO 01/74829).
WO 02/057278 describes paracyclophane ligands structurally related to the paracyclophane bis(phosphines) where the phenyl groups bound to the phosphorus in the [2.2]paracyclophane structure are replaced by oxygen, nitrogen, chloride or hydrogen atoms. These ligands are depicted below;

Rh, Ir and Ru catalysts derived therefrom were used in asymmetric hydrogenation reactions.
Whereas the paracyclophane ligands described are effective for many asymmetric transformations there is still a need to improve the activity and selectivity of catalysts derived from them over a broader range of reactions and substrates. In addition, the paracyclophane ligands generally require lengthy and expensive resolution techniques in order to provide them in high enantiomeric purity for preparing catalysts for asymmetric transformations.
Furthermore, whereas the catalysts derived from the ligands described may be effective for providing acceptable activity and selectivity in these reactions when used as homogeneous catalysts, they are not particularly amenable to immobilisation on solid supports. The fixing of homogeneous catalysts to solid supports provides the potential for extending the benefits of heterogeneous catalysts to homogeneous systems. These benefits include easier separation of catalyst and reaction products leading to shorter work up times and improved process efficiency, the potential for re-activation and re-use of the supported catalysts which are often based on expensive metals and complex ligand geometry, and the possible adaptation of the immobilised catalyst to continuous flow fixed-bed processes.